Acoustic Behavior Of Soil Reinforced With Grass Roots

Civil engineering practice has shown that vegetative roots on slopes and streambanks can substantially increase shear strength of soil and reduce erosion. Research has been done to understand and quantify the effect. Most studies have been conducted on slopes and streambanks with woody vegetation. Past research has used a perpendicular root model to predict increase in cohesion, or shear strength, due to the mobilization of roots\u27 tensile strength. Acoustics can be used to monitor internal changes of soil by interacting with soil particles and interstitial fluids. Compressional wave, or p-wave, velocity can be used to predict changes in effective stress and bulk density which can be related to geotechnical parameters such as cohesion and porosity. A literature review has concluded that an acoustic based apparatus capable of predicting increased cohesion due to grass root growth would be beneficial to geotechnical engineers and soil scientists. The goals of this study include: measuring changes in the acoustic response of soil reinforced with grass roots, modeling and measuring the effect of grass root reinforcement on the soil cohesion, and relate soil cohesion to p-wave velocity in soil reinforced with grass roots. For a laboratory experiment, two types of bermuda grass (cynodon dactylon) and bahia grass (paspalum notatum) were planted with a bare soil quadrant for control. Acoustic measurements during a year of grass root growth shoa 90% increase in p-wave velocity. A comparison of the modeled acoustic response using independently measured root density and cohesion (from direct shear tests) to in-situ measured p-wave velocity was explored. Two models were presented to explain the increase in p-wave velocity: increase in cohesion with no settlement and increase in cohesion including settlement. For the case with no settlement, the required root cohesion to explain the velocity increase was from 500 to 40,000 kpa. With the inclusion of settlement the range of required root cohesion was from 50 to 25,000 kpa

#54 - Are the kids all right? Associations among emerging adults’ experiences, anxiety, and coping.

Emerging adulthood is characterized by identity exploration, instability, self-focus, a feeling of being “in between” adolescence and adulthood, and the perception that the future holds many possibilities (Arnett, 2000). Although many emerging adults navigate this stage with minimal difficulty, some may be prone to adjustment difficulties and anxiety (Arnett, 2007). One method of coping is to minimize contact with aversive experiences (Hayes, Strosahl, & Wilson, 1999), which reduces short-term distress but may impair long-term functioning. Alternatively, mindfulness permits a client to observe a stimulus without judging or reacting to it and reduces the rigidity that underlies many disorders (Hayes, 2004; Hayes et al., 2013). It may also increase openness to experience. The aim of this exploratory study was to assess correlations among aspects of emerging adulthood, avoidance, openness, anxiety, and mindfulness. One hundred and sixty-seven students, mostly freshmen (71.7%), at a public university in the southeastern U.S. completed this study. The sample was largely female (62.9%) and Caucasian (74.9%). Roughly one third (35.3%) of the sample identified as first-generation students, and a variety of majors were represented. About one-fourth (28.7%) reported having experience with meditation or mindfulness. High levels of identification with the Instability (r = .451, p \u3c .001), and Feeling In-Between (r = .270, p = .027) facets of emerging adulthood were associated with greater experiential avoidance; greater identification with Self-Focus was negatively associated with experiential avoidance (r = -.236, p = .002). Greater identification with Identity Exploration (r = -.191, p = .014) and Instability (r = -.365, p \u3c .001) were associated with lower mindfulness. Our results suggest that mindfulness could be useful for managing distress associated with being in the transition period of emerging adulthood. We will also discuss more detailed results related to the impact of emerging adulthood on anxiety and openness

Applying the Submerged Jet Erosion Test to Embankment Dam Breach Modeling

The submerged jet erosion test (JET) is one of several methods available for quantifying erodibility of cohesive soils, a crucial input for modeling erosion and breach of embankment dams with models such as WinDAM, EMBREA (Morris 2011), and DL BREACH (Wu 2013; 2016a; 2016b). The JET was initially developed in the late 1980s as a relatively large-scale device with a 13-mm diameter nozzle creating an impinging jet that erodes a soil sample submerged in a 61-cm diameter tank. This first device was documented in an ASTM standard (D5852-1995), but the standard was withdrawn in 2016. In the last 15 to 20 years, smaller scale devices have become common, including one described as the “original JET” (6.4-mm nozzle operating within a 30.5-cm tank) (Hanson and Cook 2004) and the newer “mini-JET” (3 mm nozzle and 10-cm tank) (Al-Madhhachi et al. 2013b). New methods for analyzing the scour-vs.-time data obtained from the JET have also been proposed, some (Daly et al. 2013) based on the traditional linear excess stress equation describing the soil etachment process, and others (Al-Madhhachi et al. 2013a) based on nonlinear soil erosion models such as the mechanistic Wilson model (Wilson 1993a, 1993b). This paper provides an overview of JET history and development and then summarizes a recent study (Wahl 2021) comparing JET data analysis methods. Fifty-two JET experiments on four different soil types (lean clay, silty clay, clayey sand, and silty sand) were analyzed by nine different methods. The results give indications of the practical value of linear vs. nonlinear soil erosion models and the effectiveness of different curve-fitting methods for estimating erodibility parameters. Suggestions for the use of the JET in dam breach modeling are offered

Social Capital, Institutional Rules, and Constitutional Amendment Rates

Why are some constitutions amended more frequently than others? The literature provides few clear answers, as some scholars focus on institutional factors, whereas others emphasize amendment culture. We bridge this divide with new theoretical and empirical insights. Using data from democratic constitutions worldwide and U.S. state constitutions, we examine how social capital reduces the transaction costs imposed by amendment rules. The results indicate that constitutional rigidity decreases amendment frequency, but group membership, civic activism, and political trust can offset the effect of amendment rules. Our findings have important implications for scholars in public law, constitutional and democratic theory, and social movements

Opening the black box of mixed-metal TMP metallating reagents : direct cadmation or lithium-cadmium transmetallation?

Designed to remove some of the mystery surrounding mixed-metal TMP (2,2,6,6-tetramethylpiperidide) metallating reagents, this study examines in detail "LiCd(TMP)(3)'' in its own right. Previously established as an excellent "cadmating'' (Cd-H exchange) reagent towards a wide variety of aromatic substrates, "LiCd(TMP)(3)'' has been investigated by H-1, C-13 and Cd-113 NMR studies as well as by DOSY NMR spectroscopy. This evidence puts a question mark against its ate formulation implying it exists in THF solution as two independent homometallic amides. Exploring the reactivity of "LiCd(TMP)(3)'' with anisole as a test substrate, both experimentally by NMR studies and theoretically by DFT studies suggests a two-step lithiation/transmetallation process in which the initially formed ortho-lithiated species undergoes a reaction with Cd(TMP)(2) to form new Cd-C and Li-N bonds. For completeness, the homometallic cadmium component Cd(TMP)(2) has been comprehensively characterised for the first time including a crystal structure determination revealing a near-linear N-Cd-N arrangement

The selective oxidation of n-butanol to butyraldehyde by oxygen using stable Pt-based nanoparticulate catalysts: an efficient route for upgrading aqueous biobutanol

Supported Pt nanoparticles are shown to be active and selective towards butyraldehyde in the base-free oxidation of n-butanol by O2 in an aqueous phase. The formation of butyric acid as a by-product promoted the leaching of Pt and consequently the activity of the catalysts decreased upon reuse. Characterisation showed that the degree to which Pt leached from the catalysts was related to both the metal–support interaction and metal particle size. A catalyst active and stable (<1% metal leaching) in the aqueous reaction medium was obtained when Pt nanoparticles were supported on activated carbon and prepared by a chemical vapour impregnation method. The presence of n-butanol in the aqueous medium is required to inhibit the over oxidation of butyraldehyde to butyric acid. Consequently, high selectivities towards butyraldehyde can only be obtained at intermediate n-butanol conversion

Boletín digital Montañeros de Aragón: Epoca IV Número 51 - julio - agosto 2016

A novel layered lead titanate with the approximate composition PbTiO2(CO3)0.3(NO3)0.35(OH) has been synthesized hydrothermally under acidic conditions. The structure has been solved and refined from X-ray and neutron powder diffraction data in the space group P -3 1 m, with cell dimensions a = 5.1787(5) Å and c = 8.5222(7) Å. The titanate layers possess a gibbsite-like structure: lead cations and oxyanions such as carbonate and nitrate are included between the layers. Upon heating the solid loses water, carbon dioxide and nitrogen dioxide and converts via a poorly crystalline intermediate phase to the perovskite PbTiO3. The conversion is complete by 550°C; continued heating results in an increase in crystallinity